Abstract

We report the observation of whispering-gallery-mode lasers based on Er3+-doped ZBLAN microspheres coupled with half-tapered
and tapered optical fibers. A multimode lasing effect is observed at 1.56μm when the taper diameters are properly adjusted so that their fundamental
propagation constants match those of the resonant modes of interest. Overlap
between the pump and the laser geometrical modes is optimized by pumping at 1.48μm.

Figures (5)

Propagation constant βf (curves) of the fundamental mode in a tapered silica fiber (or
half-taper) as a function of radius r and βs (squares and circles) of WGMs with n=1 for ZBLAN spheres of different radii.

Experimental setups for coupling of an
Er-ZBLAN microspherical laser at 1.56μm with (a) half-tapered and (b) tapered fiber. In each setup the
optical spectrum analyzer (OSA) was alternatively connected to +m>0 or -m<0 channels. LDs, laser diodes.

(a) Fluorescence and (b) laser spectra
from a sphere of 53‐μm diameter. The solid and dashed lines with double arrows show the
free spectral range for the same n family. The same periodicity can be found along the horizontal
dotted lines with double arrows, which correspond to four other n families. Peaks 1, 6, and 10 correspond to TE laser modes.